1. Field of the Invention
The present invention relates to a battery-type power supply unit, and in particular to a power supply system that includes a battery assembly in which a plurality of rod-shaped battery modules are arranged so that the axes thereof are parallel to each other and, in an imaginary plane intersecting these axes, points of intersection of the axes and the imaginary plane are aligned in both the vertical direction and the lateral direction, the rod-shaped battery modules having a plurality of batteries that are connected together in series.
This type of battery-type power supply unit is mounted on a battery car, a hybrid car, a fuel cell vehicle, etc. and used as a power source. The battery concept referred to here includes those having various types of storage function such as a large capacity electric double-layer capacitor as well as a primary battery and a secondary battery.
2. Description of the Related Art
As this type of power supply system, there is a conventionally known arrangement in which synthetic resin end plates having a plurality of bus-bars embedded therein are secured by screws to the outsides of opposite end walls of a synthetic resin box, the positive electrode and the negative electrode at opposite ends of battery modules running through the box are connected to the corresponding bus-bar by means of a bolt that runs through the bus-bar and is screwed into the positive or negative electrode, and an axially middle section of each battery module is floatingly supported by means of a plurality of vibration-isolating rubber sheets. In this case, provided between two adjacent batteries of each battery module is an insulating ring for preventing a short circuit between the positive and negative electrodes (see, for example, Japanese Patent Application Laid-open No. 11-111349).
However, in the conventional system, since each battery module is supported by substantially its opposite ends, vibration causes a large amplitude of oscillation of each battery module, leading to a possibility that it might break the connection between the positive and negative electrodes of two adjacent batteries. Furthermore, since the bus-bars are fixedly embedded in the end plates, any variation in the axial dimension of the battery modules cannot easily be accommodated. Moreover, since the synthetic resin box has comparatively large dimensions and is required to have quite precise dimensions, the cost for a mold is very high, thereby resulting in an increase in the cost of the power supply system as well as causing an increase in weight.
As this type of battery-type power supply unit, there is also known an arrangement in which a dedicated cooling air duct or a plurality of cooling members are arranged within a battery assembly in order to cool a plurality of rod-shaped battery modules forming the assembly (see, for example, Japanese Patent Application Laid-open No. 10-255859).
However, it is difficult to reduce the dimensions of this conventional system since the cooling duct, etc. hinders the rod-shaped battery modules from being placed closer to each other. Moreover, the production cost inevitably increases due to a large number of components.